Never spray cleaner directly on a mirror - the drips could seep onto the silver backing and damage it. Instead, spray the cleaner on a clean soft cloth or paper towel and wipe the mirror.
Make your own cleaner. Fill a spray bottle with water and a little vinegar, surgical spirit or ammonia. Avoid strong ammonia solutions and abrasives, both of which can damage mirrors.
To hide a scratch in the silver backing of a mirror, turn it over. Cover the spot with a piece of foil, shiny side next to the glass, and then lacquer it.
